Leak detectors have been used for many applications which include detecting the concentration of specific types of gases. However, using the detector to analyze certain types of gases such as refrigerants, and the like, raises safety and environmental concerns. For example, a leak detector can be designed to detect the concentration of refrigerant gas in surrounding ambient air. This application is important, as leaking refrigerant gas can pose a threat to both health and the environment. As used herein, the term gas refers to any gaseous matter and may refer to, e.g., a combination of elemental gasses, and e.g., (ambient atmospheric gas “air”).
Previous portable leak detection equipment use Heated Diodes, Negative Corona Discharge, and other techniques. However, problems existed with these technologies. For example, short sensor life and false alarms have been usual problematic results.
Although infrared technology has existed for many years, infrared technology has not been previously used for leak detection applications for many reasons. For example, manufacturing costs would have made the use of infrared technology too expensive to be used as a leak detector.
A “closed path” type refrigerant monitor has been previously proposed for passing a modulated light beam through a gas to be analyzed and then to an optical detector, all within a closed optical chamber. The detected light is analyzed to provide information about the gas (for example, concentration). The detected light energy may be bandwidth limited such that a specific range of wavelengths is detected to facilitate analysis of particular gasses. However, there are known problems with the “closed path” monitors. For example, analysis is complicated by very little light energy being absorbed by low gas concentrations, substantial low frequency noise present in the analysis system and optical losses associated with typical optical pathways.
As one solution, modulation of the light beam has been performed at relatively high frequencies such that a reasonably large signal-to-noise ratio is maintained in the detected signal. However, there are problems with these solutions. Broadband light sources use a filament to produce spectral emission and accordingly, electronic modulation thereof at high frequencies is impractical. The filaments require too much time to heat up and cool down for high-frequency modulation. Therefore, mechanical choppers have been used to provide high-frequency modulation of the optical source. Unfortunately, mechanical choppers consume significant energy, decrease instrument reliability and increase the complexity, size and weight of instruments that they are incorporated within.
Other closed path instruments have operated without a mechanical chopper by using more powerful sources, more sensitive detectors and/or long optical paths (to facilitate increased spectral absorption by the gas analyzed) so that a somewhat lower infrared modulation frequency operation may then become possible. However, these solutions increase the size, cost and/or weight of the instruments to which they are applied.
To date there is no known type of leak detector that operates within a one second or less response time, is portable and battery powered and eliminates the problems described above with the prior art.